Background: Subacute combined degeneration (SCD) is a neurodegenerative disease caused by vitamin B 12 deficiency. The lesions mainly involve the posterior cord, lateral cord, and peripheral nerves. Occasionally, the lesions also involve brain white matter and optic nerves in severe cases. Reports of drug-induced impaired absorption and metabolism of vitamin B 12 resulting in SCD are scarce. Introduction: A patient developed SCD after long-term use of tripterygium glycoside tablets in the treatment of glomerulonephritis. However, after discontinuation and vitamin B 12 treatment with tripterygium glycoside tablet, the symptoms of SCD were significantly resolved. Conclusion: Drug-induced SCD is a less commonly reported cause of the disease. Tripterygium glycoside tablets can induce adverse reactions in the digestive system, causing damage to absorption and metabolism of vitamin B 12 . Physicians should be aware of the possibility of tripterygium glycoside tablet-induced SCD after excluding more common causes such as inadequate dietary intake and impaired absorption due to gastrointestinal diseases or genetic disorders. ? 2019, Fondazione Società Italiana di Neurologia.